In recent years, thin client systems have been drawing attention in which client environments are aggregated on a server in terms of security. As shown in Patent Literature 1, there exists among thin client systems a session management system which with a client environment, a user and a user terminal correlated, sets and manages which user is allowed to use which client environment from which terminal on a server side in the lump.
As related art, Patent Literature 2 discloses a remote connection system. The technique recited in the Patent Literature 2 is to generate a virtual client environment based on a use time set on a user basis and after confirming that the environment generated is no longer used by a user after a lapse of the use time, release resources of the generated virtual client environment. This enables effective use of server resources without wastefully consuming the same. The user is also enabled to spontaneously use a client environment because his/her own client environment is prepared before the use time starts.                Patent Literature 1: 2007-334686        Patent Literature 2: 2006-091954        Patent Literature 3: 2007-156588        Patent Literature 4: 2007-293905        
While in the session management system recited in the Patent Literature 1, since a virtual client environment can be unlimitedly generated as far as resources permit, no client environments used by users overlap with each other, in an actual thin client system and the like, there is a case where limited resources should be effectively used by a plurality of users for a physical reason or other.
In a case where the same client environment is used by a plurality of users, the technique recited in the Patent literature 1 has a problem that a certain client environment being used by a user first is not available for a user who wants to use it later. Another problem is that because a client environment is used at a remote place, it is difficult to coordinate use time or a period of use among users.
The technique recited in the Patent Literature 2 also has the same problem as that of the Patent literature 1 because it is premised on that release of a virtual client environment is executed on condition that no user is using the client environment in question.